The North Carolina Mental Retardation Research Center (MRRC) represents a diverse and coordinated programmatic endeavor to advance knowledge concerning the etiology and treatment of mental retardation. The causes of mental retardation and developmental disabilities are multiple. The few hundred suspected or identified causes of mental retardation almost certainly represent only a minor fraction of the total number of causes. Such causes have traditionally been divided into biological and psychosocial. Many moderate to severe conditions of mental retardation have biological causes identifiable with the currently available technology, while biological causes of the majority of less severe mental retardation are unknown within the limits of available knowledge and technology. The boundary between biological and psychosocial factors in mental retardation is getting less distinct not only because progress in biological sciences can identify more causes but more importantly because there is increasing awareness of the importance of interactive influence of psychological events on biology and of biological illnesses on psychological consequences. This broad-based approach remains the guiding principle of the MRRC. Thus, our research programs encompass the broadest range of concepts, disciplines and methodologies from social and behavioral sciences to fundamental molecular genetics and developmental neurobiology. The majorities of the research projects in the MRRC are conducted in two University Centers: the Brain and Development Research Center (BDRC, Director: Kunihiko Suzuki) and the Frank Porter Graham Child Development Center (FPG, Director: Donald Bailey). The MRRC operates as an integral program that seeks to establish an optimal interdisciplinary environment by providing an Administrative Core and four scientific core units: the Computer Support Core (Director: Richard Mailman), the Design and Statistical Computing Core (Director: Ronald Helms), the Observational Methods Core (Director to be named) and the Morphology-Pathology Core (Directors: Kinuko Suzuki and Thomas Bouldin). The last two Core Units are being proposed for scientific reasons as new Core facilities to replace two existing Core Units. These research efforts are augmented by existing training programs in mental retardation and related fields, a State- supported Genetic Counseling Program, and a visiting lecturer seminar series initiated during the current funding period (Hal Robinson Distinguished Lectureship). The UNC-Chapel Hill and the State of North Carolina provide extensive support to the MRRC. By efficiently coordinating specialized core support services and by providing a common administrative framework to these diverse research programs, the MRRC achieves a cost-effective means for conducting research that seeks for eventual understanding, treatment, and prevention of mental retardation.